How can a tree be stressed?
Like people, trees are stressed by unfavorable conditions and disease. Just like your body gets stressed when you get sick, trees get stressed when they’re sick. In a similar way, just like you could be stressed by unfavorable conditions (like being stuck at an airport), trees can also be stressed by unfavorable conditions. Of course, for trees unfavorable conditions are a little different. Trees are stressed by drought, unusual temperatures, insects, and many other environmental problems.

How does a tree take an aspirin?
Trees don’t actually have to take an aspirin. Whenever they’re stressed, they make it themselves. Wouldn’t that be nice?

Why aspirin? It’s not like a tree can get a headache.
Just as humans often use aspirin when they’re sick, trees make aspirin when they’re not feeling well. Trees can get sick from germs just like humans (though with different germs and symptoms). A tree also makes aspirin to deal with adverse conditions.

Do all trees make aspirin?
So far the only trees that have been found to make aspirin are walnut trees. But they’re also the only trees that have been studied! So it’s possible that many trees make aspirin to deal with stress.

Ok, that’s cool. But so what?
The trees also use the aspirin as an early warning system. Trees actually emit aspirin when they begin to get stressed as a way to tell other trees – hey, we’ve got a problem! If farmers can detect this signal they too will know early on that something is wrong with the trees. This can help farmers ‘treat’ trees more effectively. For example, if there is an insect attacking the plants, farmers could catch the infestation earlier. This would allow farmers to use less pesticide, since the problem would not yet be wide-spread, and farmers would be able to catch the infestation before the trees are extensively damaged.

THE BOTTOM LINE
Humans and trees are less different than we would seem: we both use aspirin to treat what ails us. And if farmers can detect the aspirin that the trees emit they can treat the trees earlier.